A grub is the presumed larval stage of the swarm, first encountered in SynTek Residential of Jacob's Rest. It is about as large as a marine's foot and is attracted to marines, but is incapable of harming them. Grubs come in sacs of about a dozen, which open up upon fire or when a marine is nearby.
- Grubs can be killed by weapons fire, melee attacks, or by simply walking over them.
- The Tesla Cannon will lock onto Grubs, so avoid using it when there are no other alien types present to save on ammo.
- Killing 100 Grubs earns the Bug Stomper achievement.